The present invention relates generally to the application of cable ties to wire bundles or the like and specifically to a tool that automatically dispenses, conveys and applies discrete cable ties to wire bundles or the like, where the cable ties are provided on a continuous ribbon.
Prior automatic cable tie installation tools have utilized a cartridge to contain a number of discrete cable ties and provide the cable ties sequentially to a dispenser mechanism in the tool. The use of a cartridge to feed discrete cable ties to an automatic cable tie installation tool presents inherent limitations and operational difficulties that limit the efficiency of the tool.
Any tool utilizing a cartridge has the inherent limitation of only being able to apply as many cable ties as the cartridge is designed to hold. Application by the tool of all the ties in the cartridge necessitates the exchange of the empty cartridge for a loaded cartridge or the manual refilling of the empty cartridge. Practical design constraints dictated by the dimensions of the cable ties and the need for a portable and easily operable automatic tool have limited the number of cable ties carried in an individual cartridge to approximately one hundred cable ties.
Prior tools also require the cable ties to be loaded into each cartridge in a specific and consistent orientation, requiring careful and time consuming manipulation of individual cable ties during the cartridge loading operation.
Compounding the above described inefficiencies is the fact that cartridge supplied tools inherently have complex mechanisms to allow the detachable mounting of a cartridge and to sequentially dispense cable ties from the cartridge. Such mechanisms must meet close tolerances in manufacture and fit and must be carefully operated and maintained in order to provide error free operation. Due to these constraints, prior tools have failed to operate flawlessly during the attachment of new cartridges. The tools often will jam during the loading of a cartridge requiring the waste of operator time to unjam and properly reload the tool.
All of the above problems contribute to a loss of overall efficiency in the prior automatic cable tie installation tools; a significant portion of an operator's time being devoted to the loading of cartridges instead of to the application of cable ties.
Additional problems inherent in supplying cable ties by cartridge include the increased costs due to manufacture, storage and disposal of the cartridge.
Another problem of prior art tools is the use of mechanical or pneumatic logic to control the many sequential operational steps necessary to dispense, convey and supply a cable tie. The use of mechanical and pneumatic systems to control the various actions of a tool requires the use of a large number of interacting valves, linkages, etc. with the concomitant expense of manufacture and expense of maintenance that a tool having a large number of interacting mechnical components entails.
Additionally, pneumatic logic systems are inherently sensitive to variance in pressure of their control fluid or to contamination of their control fluid, either of which can cause timing errors in the control system. Due to the high speed at which automatic cable tie installation tools complete a cycle, small errors in control logic timing can result in the failure of the control logic to actuate the mechanisms of the tool in proper operational order with the attendant failure of the tool.
Prior automatic cable tie installation tools have pneumatically conveyed the ties provided by the cartridge through a tube at high velocity to a remote hand tool where the tie is positioned around a bundle of wire and installed. Successful receipt of the tie by the remote tool requires the tie to be brought to rest at the correct position within the remote hand tool, relative to the other working mechanisms of the hand tool. Typically, a head stop or abutment has been provided to stop and correctly position the tie. The head stop being positioned to inhibit the forward motion of the tie by interferingly stopping the head of the tie.
The problem of intermittent destruction of the cable tie due to the abrupt impact of the tie head against the head stop was experienced and was addressed in the commonly assigned U.S. Pat. No. 4,004,618. U.S. Pat. No. 4,004,618 discloses a pair of resilient steel arms that act as a brake to decrease the velocity of the tie before it strikes the head abutment thus decreasing the probability of tie fragmentation upon impact. The arms were also positioned to prevent retrograde movement of the tie after it had passed by the arms.
Although the above mentioned disclosure describes one structure that will decrease the probability of impact induced destruction of a pneumatically delivered cable tie, certain problems are encountered with the use of resilient steel arms. One problem is that the continued flexing of the steel arms caused by a passing tie results in outward deformation of the arms destroying their braking efficiency and eventually results in failure of the steel arms due to fatigue. Additionally, although the arms prevent retrograde movement of the tie, they do not positively lock the tie in position. Thus, a need exists for an improved tie braking and tie positioning mechanism, that will have increased efficiency, reliability and simplicity.